1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and a substrate processing apparatus, and more particularly, to a method of manufacturing a semiconductor device and a substrate processing apparatus, which are designed such that formation of boron (B)-compound on a nozzle of the apparatus can be prevented when substrates are processed.
2. Description of the Prior Art
To dope a wafer (silicon substrate) with boron (B) in a general decompression chemical vapor deposition (CVD) apparatus, B2H6 (diborane) gas can be used. For example, when a boron-doped silicon film is formed, B2H6 and a silicon (Si)-compound (silicon-containing gas as a constituent element such as SiH4, Si2H6, and SiH2Cl2) are supplied, and when a Boron-doped silicon germanium film is formed, a germanium (Ge)-compound (Ge-containing gas as a constituent element) is supplied together with B2H6 and a Si-compound, so as to form a B-doped film on the surface of a wafer. Although BCl3 can be used as a boron doping gas instead of B2H6, the use of B2H6 is preferable in that B2H6 does not cause metal contamination because B2H6 does not include chlorine (Cl), and moreover, B2H6 is inexpensive.
In the case where a plurality of wafers are processed by using a vertical or horizontal apparatus, most of B2H6 is consumed by wafers disposed at the upstream side of a process chamber because B2H6 is very reactive, and thus wafers disposed at the downstream side of the process chamber are not properly doped. For this reason, a plurality of nozzles are installed in a manner that the nozzles are disposed at the downstream side as well as the upstream side, so as to improve the uniformity of inter-wafer boron concentration.
However, in the case where nozzles are disposed as described above, if nozzles disposed at a high-temperature region of a process chamber is heated to about 300° C. or higher, B2H6 decomposes thermally in the nozzles to cause deposition of B-compound films on the inner walls of the nozzles. That is, B2H6 is consumed in the nozzles and may not be introduced into the process chamber. Along with this problem, there also arise other problems, such as difficulties in controlling and maintaining the uniformity of inter-wafer boron concentration, and generation of particles caused by B-compound films stripped from the inner walls of the nozzles.